1. Field Of Use
The present invention relates to a mechanism for controlling the relative space created between two components, in general, and to a height adjustment mechanism for controlling the height of a chair back and the relative spacing between a chair seat and the chair back, in particular.
2. Brief Description Of The Prior Art
Prior art chair back height adjustment mechanisms are available in various forms. In some, a manually operable screw releasably secures a slidably adjustable back at desired positions on an upwardly extending J-bar which is part of a chair frame. In others, a manually operable rack-and-pinion-type or ratchet-type mechanism enables chair back height adjustment. Such prior mechanisms are typically relatively complex in constructions, costly to manufacture, trouble-prone and unreliable in use.
U.S. Pat. No. 4,102,549 (Morrison et al) assigned to Knoll International, Inc., relates to an adjustable back support using a position stop of flexible material which may be flexed from an engaged position in which the back support of the chair is locked by the position stop to a disengaged position in which the back stop is movable.
U.S. Pat. No. 4,639,039 (Donovan) relates to a height adjustment mechanism for a chair back. The Donovan patent discloses an adjustment mechanism for manually positioning and releasably locking a chair back in a desired vertical position relative to a chair seat. The mechanism is made up of a guide rigidly secured to an upright back support frame of a chair and a channel rigidly secured to the back. The channel is mounted for vertical sliding movement on the guide. The channel includes a slot having a plurality of vertically arranged notches along one vertical edge of the slot, and three other cam surfaces to complete a closed geometric figure.
A latch bar is pivotally mounted on a pivot pin on the guide and has a latch pin extending into the slot. A torsion spring mounted on the guide between the guide and channel biases the latch bar in a latched position, wherein the latch pin releasably engages a notch to maintain the back at a selected height. Manually raising the back slightly above the highest latched position causes the latch pin to pivot the latch bar to a spring biased unlatched position. Then, manually lowering the back to its lowest position causes the latch bar to pivot into an unlatched position, where the latch pin engages the highest notch to maintain the back in its lowest position.
U.S Pat. No. 4,749,230 (Tornero) relates to a height adjusting device for manually locating and automatically locking a chair back at a desired vertical position relative to a chair seat. The device generally comprises two guided and slidably interlocking plates and one lock pin. The lock pin is free to move within a sinus-shaped slot defined within one plate and forced therewith from one locked position to a stand-by position, or to an unlocked position by the cam action of any of a plurality of notches and inclined surfaces of a slotted cam contained on the other plate. According to the Tornero patent, the device is characterized by the absence of springs or other supplementary biasing means.
There is thus a need for height adjustment mechanism for adjusting the relative distance between a chair seat and a chair back where the mechanism is simple, easy to use and, at the same time, highly reliable. The present invention is directed toward filling that need.